Arthroplasty spinal prosthesis and insertion device

ABSTRACT

An arthroplasty spinal prosthesis with first and second vertebra contacting members that are configured for engaging opposing vertebrae An articulation is supportively associated with the contacting members to allow relative pivotal and translational motion therebetween over anterior-posterior and lateral pivotal axes, and over anterior-posterior and lateral translational axes. This motion allows the opposing vertebrae to pivot and translate with respect to each other. The articulation is configured to permit translational movement substantially uncoupled from the pivoting movement.

FIELD OF THE INVENTION

The present invention relates to a prosthesis for articular associationwith the bone structure of a patient, and more particularly to a spinalprosthesis.

BACKGROUND OF THE INVENTION

Procedures exist for replacing diseased intervertebral disks in whichthe disk material is typically removed from between adjacent vertebralbodies, and the adjacent bodies are fused. This has been done with acage filled with bone or bone forming proteins placed in between thebodies to fix them to each other, generally to support and promotefusion between the adjacent vertebrae.

In arthroplastic procedures, a pivotally articulated prosthesis isimplanted between the vertebrae in the site of the diskectomy. Forexample, U.S. Pat. Nos. 5,425,773 and 6,063,121 disclose intervertebralarthroplasty devices that use different ball and socket arrangements topermit movement between the vertebrae. The ball and socket is disposedat center between surfaces of plates that are placed against thevertebrae. The intervertebral disk prosthesis disclosed in U.S. Pat. No.5,556,431 has a core and endplates with a spherical articular surface.The core has an edge rim that limits the range of movement.

Other teachings also provide for translational movement between thevertebrae. U.S. Pat. No. 6,113,637, for instance, shows anintervertebral joint with a ball component engaged with a vertebra andwith a trough component, which is engaged with another vertebra. Thetrough component has a flat portion that allows translation of the ballcomponent on one axes. A prosthesis disclosed in Patent ApplicationPublication US 2002/0128715 shows a flexible central body between tworigid opposing shells to allow combined translation and bending.

There is a need for an improved disk prosthesis that provides improvedarticulation between the vertebrae between which it is implanted.

SUMMARY OF THE INVENTION

The present invention relates to an anthroplasty spinal prosthesis forimplantation in a human or animal to provide improved implantationlongevity and articulation kinematics similar to the tissue beingreplaced. The preferred embodiment of the prosthesis has first andsecond bone or vertebra contacting members configured for engagingopposite articulated bones, preferably bones of the axial skeleton, suchas two vertebrae or a vertebra and the skull. An articulation issupportively associated with the contacting members to allow relativepivotal and translational movement therebetween. This movement ispreferably over anterior-posterior and lateral pivotal axes and overanterior-posterior and lateral translational axes. The movement betweenthe contacting members allows the opposing vertebrae to pivot andtranslate with respect to each other. Also, the preferred articulationis configured to permit the translational movement to occur withoutcoupling or causing a pivotal movement, although another embodiment canprovide the coupling if desired. Preferably, the amount of translationalor pivotal movement is substantially not affected or dependent on theother of these movements. Thus, the contacting members can translateregardless of whether they also pivot, and they can pivot regardless ofwhether they may also translate. Similarly, the preferred articulationallows the contacting members to rotate axially with respect to eachother, and this rotation is also not substantially coupled by thearticulation with the pivotal or translational movement. Preferably, theprosthesis also allows synchronous movements of flexion and translationas well as movement simultaneously in rotation bending, andflexion/extension.

The preferred articulation is configured for limiting the translationalmovement along both translational and pivotal axes to withinpredetermined ranges. The preferred translational axes extendssubstantially through at least one of the pivotal axes, and mostpreferably both anterior-posterior and lateral translational axes extendsubstantially through both anterior-posterior and lateral pivotal axes,with regard to one or both contacting members.

Preferably, the articulation has first and second articulation portionsthat are moveably associated with each other. The first articulationportion is pivotally associated with the first contacting member, andthe second articulation portion is pivotally associated with the secondcontacting member. The first articulation portion or first contactingmember can define a protrusion, while the other defines a recessconfigured to receive the protrusion to pivotally associate these twoelements. A similar structure with a protrusion and recess can also beprovided for the second articulation portion and second contactingmember. At least one of the recess and protrusion is preferably taperedsubstantially about a spinal axes that extends axially between theconnecting members. The articulation portions also preferably compriseblocking members that are juxtaposed radially with respect to the spinalaxes to abut each other for limiting the translational movement betweenthe articulation portions to provide semiconstrained translation. Theblocking members can include a key that extends from one articulationportion and that fits into a keyway defined in the other articulationportion. The association between the key and keyway allows translationalmovement, and the keyway provides an edge wall disposed to block thetranslational movement of they key. Preferably, the edge wallsubstantially surrounds the key, and both the edge wall and key areannular about the spinal axes. Most preferably, the edge wall comprisestwo edge walls that are disposed on opposite sides of the keyway so thatthe key and edge wall concurrently contact each other at at least twolocations to block the translational movement. In one embodiment, thekey and keyway can have a dovetail configuration or cross-section toaxially retain the key within the keyway at a limit of the translationaltravel.

The preferred articulation portions are ring shaped with a hollowcenter. A retaining member can be associated with the contacting membersto extend through the hollow center of the articulation portions toprevent the escape of the articulation portions, such as when subjectedto extreme trauma. The retaining member can comprise, for example asuture or other flexible material or a post extending through the hollowcenter of at least one of the articulation portions. Suture openings canbe provided through the contacting members and any structurestherebetween to allow the suture to extend from one contacting member tothe other and to be fastened thereabout.

The first and/or second contacting members of the preferred embodimentinclude a fastener mount portion that is configured to attach a bonefastener from the prosthesis to the vertebra that is engaged therewith.Vertebral contacting surfaces of this contacting member are disposed andoriented to position the body of the engaged vertebra such that theapophyseal ring of the body is disposed with respect to the fastenermount portion in an attachment position for attaching the fastener fromthe fastener mount portion through the apophyseal ring. The fastenermount portion can define an opening to receive a threaded surgicalfastener, such as a surgical screw, and which can be made of metal,polymer, or absorbable material. The preferred fastener mount portion isoriented for inserting the fastener diagonally into the apophyseal ring.Also, a plurality of fastener mount portions can be provided to insert aplurality of fasteners through the apophyseal ring. Additional fastenermount portions can be provided to insert other fasteners in otherorientations and locations into the vertebra, such as oblongly orlaterally, which can be beneficial for use in different parts of thespine, for instance with L1 or L2 vertebrae.

The vertebral contacting surfaces of the preferred embodiment areoriented to capture axial and radial surfaces of the vertebral body toposition the apophyseal ring in the attachment position. The axialcontacting surface is preferably oriented to abut and support an axialface of the vertebral body, while the radial contacting surface ispreferably configured to abut a radial side of the vertebral body. Anapophysis grove can be defined between the axial and radial contactingsurfaces to receive the apophyseal ring. A fastener mount portion ispreferably configured to direct the fastener into the apophysis grove,to ensure that the fastener penetrates the apophyseal ring.

An embodiment of the prosthesis has at least one of the contactingmembers and articulation that is made of radiolucent material to reduceor avoid creating an artifact on an MRI, computed tomography or an x-rayor otherwise significantly obscure or block an image being produced.Preferably, the entire prosthesis, and at least major portions thereof,such as the contacting members and articulation and optionally thefasteners, are substantially radiolucent. Radiopaque markings can beprovided that are visible on an MRI, an x-ray, a CT scan, or otherimaging systems to help displace and position the prosthesis duringimplantation, or to monitor its position thereafter. The prosthesis canbe configured to deliver a treatment, such as by comprising anddelivering an antibiotic, protein, or biologically active substance tothe implantation site. This substance can be impregnated in the materialof one or both of the contacting members, Polymethylmethacrylate (PMMA)can be used for a slow release of the substance.

Some embodiments of the inventive prosthesis have a vertebral bodyprosthetic portion that is configured to replace at least a portion of avertebral body of the patient. The body prosthetic portion is fittedbetween the contacting members and is articulably associated therewithvia articulations, such as the articulation portions described.Consequently, this prosthesis has portions configured to replace both atleast a portion of a vertebral body and two adjacent disks. Thisprostheses can be used in an implantation site between two nonadjacentvertebrae, and is preferably configured to carry the spinal loadsthrough the contacting members, articulations, and vertebral bodyportion when implanted.

A preferred prosthesis insertion device includes first and secondholding portions that have a holding position in which the holdingportions cooperatively and positively hold the prosthesis. A connectingmember is associated with the holding portions to selectively maintainthe holding portions in the holding position and for releasing themtherefrom. In the holding position, the holding portions cooperativelycapture the prosthesis sufficiently to prevent removal thereof from theholding portions and to maintain a predetermined orientation between thearticulated portions of the prosthesis, such as the contacting member.When released from the holding position, the holding portions areconfigured to release the prosthesis.

Preferably, the connecting member comprises a hinge that pivotallyconnects the holding portions. This hinge can be part of a scissorlinkage for moving the holding portions to and from the holdingposition. Alignment bores can be provided in the holding portions,including bores formed cooperatively by aligning groves in each holdingportion when they are placed in the holding position. These bores can beconfigured for guiding a drill, such as by inserting a drill guidetherein, or for guiding a fastener or fastener driver to a predeterminedposition and orientation with respect to the prosthesis.

The present invention thus provides an improved prosthesis andimplantation device for use in the spinal column with improved wear andarticulation characteristics.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1-3 are perspective, exploded, and side cross-sectional views,respectively, of a preferred embodiment of an intervertebral diskprosthesis constructed according to the present invention;

FIGS. 4 and 5 are anterior and posterior views, respectively, of anotherembodiment of a prosthesis with three bone-screws for fastening to eachvertebra;

FIGS. 6 and 7 are exploded and perspective views, respectively, ofanother embodiment of a prosthesis that does not employ bone fasteners;

FIGS. 8 and 9 are exploded and cross-sectional views, respectively, of aprosthesis embodiment with a resilient shock-absorbing member betweentwo vertebra contacting members;

FIG. 10 is a cross-sectional view of another embodiment with upper andlower shock absorbing members;

FIGS. 11 and 12 are exploded and perspective views, respectively, ofanother embodiment of a prosthesis that uses a dovetail configurationfor limiting translation between articulation portions, and which haschannels to promote lubrication of the articulation;

FIG. 13 is a cross-sectional view of the articulation portions thereof;

FIG. 14 is an anterior perspective view of a prosthesis embodiment witha fastener-locking mechanism;

FIG. 15 is an exploded view showing the locking mechanism thereof;

FIGS. 16 a-e shows several prostheses that can be assembled from a kitprovided in accordance with the present invention;

FIG. 17 is a perspective view of an inventive broach configured fordetermining a desired prosthetic assembly;

FIGS. 18 and 19 are perspective and exploded views of an embodiment of aprosthesis for use with a corpectomy procedure;

FIG. 20 is an exploded view of another embodiment of a prosthesis foruse with a corpectomy procedure;

FIG. 21 is a perspective posterior view of an insertion device holding aprosthesis for implantation;

FIGS. 22 and 23 are side views of a holding member of the insertiondevice, showing the use of a drill guide and a fastener driver, with theopposing holding member of the insertion device not shown for clarity;and

FIG. 24 is a top view of a preferred embodiment of the insertion device.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring to FIGS. 1-3, the preferred embodiment of the invention is avertebral disk prosthesis 10, which includes top and bottom contactingmembers 12,14. The contacting members 12,14 preferably include top andbottom endplates. Each contacting member 12,14 of this embodiment has amain body support portion 15 that includes an axial vertebral contactingsurface 16 facing axially and configured for engaging axial superior orinferior faces of opposing vertebral bodies when implanted along aspinal column.

The vertebral contacting surfaces 16 preferably have a texture, shape,and/or treatment to promote engagement with the face of the engagedvertebral body. The texture shown provides an uneven surface to improvegripping against the vertebral body and to promote bone ingrowth intothe surfaces 16. The uneven surface can include a series of angular orpointed shapes or other protrusions and indentations, such as pyramids,scales, or tetrahedrons, or trebecular metal for example. Alternativelyor additionally, the axial contacting surfaces 16 can have other surfacetreatments, and can be coated, for instance, with plasma sprayedtitanium, calcium phosphate, hydroxyapetite, or proteins. In someembodiments, the surfaces can be smooth.

The uneven surface is preferably disposed to engage and grip the concaveinterior portion of the axial face of the vertebral body, mostpreferably within the apophyseal ring. To best engage this interiorportion, the axial contacting surfaces 16 are preferably convex andcurved along one or two radial directions, preferably along ananterior-posterior direction and a lateral direction. The contactingsurface preferably has an overall rounded shape to prevent expulsion andincrease contact. The rounded shape can improve and provide immediatestability to prevent expulsion.

The contacting members 12,14 also preferably include flanges 18 thatextend axially at an angle to the axial vertebral contacting surfaces 16and include radial vertebral contacting surfaces 20. The radialcontacting surfaces 20 are preferably oriented to abut the radial wallof the vertebra body. Most preferably, the radial contacting surfaces 20are concave to follow the shape of the radial wall. In a preferredembodiment, the flanges 18 are disposed and configured to contact thefront radial side of the vertebral body, but in an alternativeembodiment, the flanges 18 and radial contacting surfaces can beoriented to contact another radial side of the vertebral body, such as alateral side or a portion partway between a lateral side and theanterior or posterior side, such as at an oblique side of the wall.

A fastener mount portion 22 is preferably provided for attaching a bonefastener 24 thereto, such as a bone screw or other bone fastener. Thefastener mount portion 22 preferably defines an opening 24 to receive athreaded portion 26 of the fastener 24 for insertion into the vertebra,and has a fastener seat 28 to align and seat a head 30 of the fastener24.

The contacting surfaces 16,20 are disposed and oriented to position thevertebral body to be engaged with the prosthesis 10 to positionapophyseal ring of the body in an attachment position with respect tothe fastener mount portion 22. In the attachment position, shown in FIG.3, the apophyseal ring 34 of the vertebral body 32, shown in phantomlines, is disposed with respect to the fastener mount portion 22, suchthat the fastener 24 is aligned to extend through the apophyseal ring 34to attach the contacting members 12,14 to the vertebra 32. Thispositioning of the fastener is desired since the apophyseal ring 24 isthe strongest part of the vertebral body and it ensures a strong, robustand immediate attachment of the prosthesis 10 to the vertebra 32. Thefastener 24 preferably extends diagonally into the apophyseal ring,preferably at an angle 38 of at least about 10°, more preferably atleast about 30°, and most preferably at least about 40° with respect tothe spinal axes 36; and preferably at most about 80°, more preferably atmost about 60°, and most preferably at most about 50° thereto.

The contacting surfaces 16,20 of the contacting members 12,14 alsopreferably define a apophysis groove 40 defined between the axial andradial contacting surfaces 16,20 to receive the apophyseal ring 34. Theapophysis groove 40 has a curvature around the spinal axes 36 configuredto follow the general shape of the apophyseal ring 34. The dimensions ofthe apophysis groove 40 are selected to receive the apophyseal ring 40therein so that the axial and radial contacting surfaces 16,20 can abutthe axial and radial surfaces of the vertebral body 32. The fastenermount portion 22 is preferably disposed with the opening 24 extendinginto the apophysis groove 40 to direct the fastener 24 into theapophysis groove 40 as well.

Although the apophysis groove 40 can be made to extend into only theaxial or the radial contacting surface 16 or 20, in the preferredembodiment, the apophysis groove extends into both the axial and radialcontacting surfaces 16,20. The radial width 42 and axial height 44 ofthe apophysis groove 40 are preferably between about 2 mm and 5 mm, andmore preferably between about 2.5 mm and 4 mm. The height and width canhave the same or different dimensions from each other. Most preferably,the height 44 of the apophysis groove 40 is sufficient to position theapophyseal ring 34 to extend vertically within the groove 40 in theflange 18 at least up to about half the height of the fastener 24 toensure the fastener 24 transects the apophyseal ring 34. In thepreferred embodiment, the apophysis groove 40 is configured so that itssurface abuts and supports the apophyseal ring 34, although in anotherembodiment, the apophysis groove 40 provides a clearance from theapophyseal ring 34. The dimensions of groove 40 can be selected to movethe center of rotation posteriorly in the disk space. Preferably, theaxial and radial contacting surfaces 16,20 are oriented to capture axialand radial surfaces of the vertebral body 32 for positioning theapophyseal ring in the attachment position.

The prosthesis 10 includes an articulation 46 that articulably connectsthe contacting, members 12,14. The articulation 46 preferably includesupper and lower articulation portions 48,49 that are received inarticular cavities 50 defined on the opposite side of the main supportportion 15 from the axial contacting surface 16 of each contactingmember 12,14. The articulation portions 48,49 of the preferredembodiment are preferably ring shaped disks, preferably being rounded,preferably circular along a generally radial plane, with a hollowcentral, axial opening 52.

Outer bearing surfaces 54 of the articulation portions 48,49 aresupportively associated with bearing surfaces 56 of the cavities 50. Thecorresponding bearing surfaces 54,56 are preferably curved incross-section, although one set may be curved, while the abuttingbearing surface is generally straight. The bearing surfaces 54,56 areconfigured and associated to allow the contacting members 12,14 to pivotabout the articulation portions 48,49, preferably about more than oneaxes. When the prosthesis is loaded by supporting the adjacent vertebraeengaged therewith, a clearance 58 is preferably provided on an axialside between the articulation portions 48,49 and the contacting members12,14. This clearance can be provided due to the axial taper of one orboth of these members. The bearing surfaces 54,56, which preferably facepredominantly in a radial direction but are inclined with respect to theaxial and radial direction, are in supportive abutment with each other,preferably radially outside the clearance 58 area.

The articulation 46 is preferably configured to permit independent andconcurrent anterior-posterior flexion and extension and lateral bendingand preferably also axial rotation between the contacting members 12,14.The range of flexion/extension and lateral bend is preferably at leastabout 5°, more preferably at least about 8°, and most preferably atleast about 10°; and is preferably up to about 20°, and more preferablyup to about 16°. The pivoting is preferably limited by the abutment ofedges of the contacting members 12,14, or by the articulation portionsreaching the ends of possible travel within the cavities 50, althoughanother mechanism can be provided. Other ranges can be provided fordifferent needs in different locations of the spine.

The articulation portions 48,49 are preferably are configured totranslate with respect to each other, preferably by sliding, to allowrelative translation between the contacting members 12,14. Timer bearingsurfaces 60 of the articulation portions 48,49 are preferablysupportively and slidingly associated with each other to allowtranslation, preferably along more than one axes. In the embodimentshown, the inner bearing surfaces 60 are substantially planar.Preferably, one or both translational axes extend substantially throughor very near the pivotal axes.

Articulation portion 48 defines a keyway channel 62 that receives a key64, which protrudes from the inner bearing surface 60. The keyway 62 isradially wider than the key 64 by an amount selected to permit and limitthe translation between the contacting members 12,14. Both the keyway 62and key 64 are preferably annular, and most preferably circular. The key64 and keyway 62 are preferably configured such that at the limit of thesliding travel, the key 64 and the wall of the keyway 62 abut at twopoints, such as at opposite ends of the respective annuli formed by thekeyway 62 and key 64. Alternatively, a single point of contact can beused to block excessive translational movement. With this construction,the key 64 and keyway 62 are juxtaposed radially with respect to thespinal axes to function as blocking members.

The allowable translation can occur on more than one axes independentlyand simultaneously. The preferred embodiment allows anterior-posteriortranslation and lateral translation in ranges that are preferably about1 mm to 2 mm for a cervical prosthesis, about 1 mm to 2.5 mm for athoracic prosthesis, and about 2 mm to 4 mm for a lumbar prosthesis.

To prevent the articulation portions 48,49 from exiting the spacebetween the contacting members 12,14 in a extremely traumatic event, thecontacting members 12,14 have posts 66 that extend into the articularcavities 50 and axial openings 52. Under normal flexion, extension, andbending motion limits, the articulation portions 48,49 are retained inthe articular cavities 50 and are prevented from escaping into the spacebetween the radially outer edges of the contacting members 12,14 by theassociated shapes of the contacting bearing surfaces 54,56. The posts 66are most preferably configured to abut the edge of the axial openings 52at the limit of pivotal motion, while the bearing surfaces 54,56 arealso in contact.

Axial rotation between the contacting members 12,14 is preferablyprovided by rotational sliding between the contacting members 12,14 andthe articulation portions 48,49 and/or between the articulation portions48,49 themselves. In the preferred embodiment, the axial rotation isunlimited, and the patient's facet joints, ligaments, annulus, andtendons provide axial rotation stability.

In the preferred embodiment, the contacting members 12,14 arearticulated to allow relative pivotal and translational motiontherebetween over anterior-posterior and lateral pivotal axes, and alsoanterior-posterior and lateral translational axes, The opposingvertebrae can thus pivot and translate with respect to each other. Thearticulation 46 is configured to permit translational movementsubstantially uncoupled from the pivoting movement. Similarly, thepreferred articulation allows axial rotation substantially uncoupledfrom the other axes of movement as well. As a result, flexion,extension, or lateral bending that is initiated in the adjacentvertebrae does not cause the articulation to induce a translation oraxial rotation, for instance, and vice versa. A movement along any oneaxes preferably does not cause the articulation to induce a movement inanother axes. This is particularly useful because normal movements inthe spine can combine variable amounts of movements along different axessimultaneously or sequentially. The prosthesis 10 can thus accommodatesynchronous, coupled movement and sequential movement along the spineover different axes. Additionally, due to the construction of thepreferred articulation, the contacting members can have pivotal andaxial-rotational axes that are displaced from each other when thearticulation is in an off-center state of translation.

Referring to FIGS. 4 and 5, another embodiment of a prosthesis 68 hascontacting members 70 with three fastener mount portions 22 on eachcontacting member 70.

A plurality of fasteners 24 is beneficial for use with less stable orweakened bone such as with ligamentous instability, i.e., whensacrificing the posterior longitudinal ligament complex. Preferably, themajority of the fastener mount portions 22 are disposed and oriented toinsert the respective fasteners 24 diagonally into the apophyseal ring.In this embodiment, fastener mount portions 22a have such aconfiguration, which fastener mounts 22 b are configured to attach afastener at a more horizontal angle into the vertebral body at aposition above the apophyseal ring. The apophysis groove 40 shownprincipally extends into the axial surface 16, and by a small amount ornot at all into the radial surface 20.

FIGS. 6 and 7 show an embodiment of a prosthesis 72 for more highlystable implantation sites, such as when sparing the posteriorlongitudinal ligament complex. In this embodiment, no fastener mountportions are provided. The ledges 74 of the contacting members 76 aresufficiently tall to engage the apophyseal ring of the engaged vertebralbody, to prevent the prosthesis 72 from sliding further into theintervertebral space and to permit subsidence. When the ledge isimplanted on the front side of the vertebral body, ledges 74 keep theprosthesis 72 from sliding towards the spinal chord. Additionally, thereis no apophyseal groove provided in this embodiment, although analternative embodiment can incorporate such a groove to positivelycapture the apophyseal ring.

A flexible sheath 78 is provided around the contacting members 76,preferably enclosing and optionally sealing: the articular space inwhich the articulation portions 48,49 are disposed. The sheath 78 canadvantageously resist or prevent debris from migrating, from the bearingsurfaces of the articulation into the body, as such debris can causeweakening of the bone. The sheath can also or alternatively beconfigured to resiliently bias the contacting members, such as towards acentral axial rotation position. Advantageously, the periphery of thecontacting members 74 can be angled to allow provide the resilientrotational bias. Other embodiments can have round contacting members,however. The membrane can also send in lubricating fluids, natural andsynthetic or to provide treatments, such as antibiotics or antiinflammatory treatments. The membrane can also prevent interposition ofsurrounding soft tissue into the device.

Referring to FIGS. 8 and 9, another embodiment of a prosthesis 80 doesnot employ posts to keep the articulation portions 48,49 from exitingthe articular cavity 50. A resilient member 82 is disposed between thecontacting members 84 to absorb axial shocks between the engagedvertebrae. The resilient member 82 in this embodiment has a doubletapered shape, with the narrowest part at the axial center thereof tocorrespond with the taper of the central opening 52 in the articulationmembers 48,49, within which opening 52 the resilient member ispreferably disposed. The resilient member is preferably made of anelastically compressible material that is significantly softer than thecontacting members 84 and articulation portions 48,49. Suitablematerials include elastomeric materials, including rubber and syntheticelastomers. A resilient member can also be employed with an embodimentwith posts 66 to provide axial compression damping.

Suture recesses or notches 86 in which suture holes 88 are disposed aredefined on the outer axial side of the contacting members 84. The sutureholes 88 extend into the articular cavity 50 and are aligned with sutureholes 88 of the opposing contacting member 84. A suture 90, preferablyof resorbable material, can be threaded through the suture holes 88 totie the contacting portions 84 together to retain the prosthesis 80 inan assembled condition, which is beneficial when certain ligaments havebeen severed for implantation, such as the annular ligament andposterior longitudinal ligament. As the tissue heals, the suture 90 candissolve when it is no longer needed for the stability of the prosthesis80. Alternatively, a non-dissolving suture can be used. If a centralresilient shock absorbing member is employed, as shown in thisembodiment, the member 82 preferably also has openings 92 through whichto thread the suture 90. A different type of retaining member to retainthe contacting members 84 together can alternatively be used. Thenotches 86 can be used for recessing the suture knot 91 or for anotherdesired purpose, such as for anchoring a bone graft.

The prosthesis embodiment 94 of FIG. 10 has resilient shock-absorbermembers 96 fitted in central recesses 98,100 of the contacting members102 and articulation portions 104. In this embodiment, the articulationportions 104 have an axially closed center, not having a central openingthat extends axially completely therethrough. The resilient members 96of this embodiment can also be employed to provide a resilient biasabout the anterior-posterior and lateral bending axes. A resilientshock-absorber can also be employed between the contacting members 102.

An embodiment of a prosthesis 106 is shown in FIGS. 11-13, in which thearticulation portions 108,110 define exterior lubrication channels 112to allow human fluid serum to enter and lubricate the bearing surfaces54,56. In an alternative embodiment, the lubrication channels areprovided in the bearing surfaces 56 of the contacting members 118, andthe articulation-portion bearing-surfaces 54 are smooth. Additionally,the key 114 and keyway 116 have dovetail cross sections to help retainthe articulation portions 108,110 from separating radially or axially ata limit of the translational movement range. In an other embodiment, oneof the radial sides of the key 114 and keyway 116 cross-sections canhave the respective tapered portion of a partial dovetailcross-sectional shape, and the other radial side can be generally flator can have a different shape.

Referring to FIGS. 14 and 15, another embodiment of a prosthesis 122 hasa fastener mount portion 120 with a locking element 124. A lockingfitting 126 is attached, and preferably fixed, to the contacting members128, for example via a tongue-in-groove fitting, with a tongue 130 and agrove 132. The fitting 126 includes a locking tab with a ledge 134 thatis sufficiently resilient and deformable to allow the head 30 of thefastener 24 to pass thereby when it is screwed into the vertebra.Preferred materials for the construction of the fitting 126 includecobalt chrome and plastics, such as polyethylene and PEEK(polyetheretherketone), or resorbable polymers. A locking ledge that isunitary with the main body of the contacting member can alternatively beused. The ledge 134 blocks retrograde movement of the fastener 24 out ofthe bone once implanted. Alternative fastener locking devices can beused, such as fasteners with compressible or expanding locking heads.

A kit is preferably provided to a surgeon with various contactingmembers 136 a-j can be provided for assembly about an articulationmember that includes articulation portions 138 to provide an assembledprosthesis for implantation. A variety of kit parts allows modularity ofprosthetic size to custom fit the device to the patient's evacuated diskspace. Examples of prostheses that can be assembled from the kit areshown in FIGS. 16 a-e. Several broaches such as the broach 140, shown inFIG. 17, can be inserted into the disk space after performing adiskectomy to determine the appropriate height and lordotic angle forthe assembled disk prosthesis to be implanted. The broach also distractsthe disk space, allowing nerve root decompression and loosening of theligaments adjacent to the disk space, i.e., annular ligament andposterior longitudinal ligament. The preferred broaches 140 have aprobing end 142 that has contacting surfaces in the same general shapeas of various assembled prosthesis that can be assembled from the kitparts. A ledge 144 extends adjacent an axial contacting portion 146 tostop the insertion of the probing end 142 at the appropriate location.At the opposite end from the probing tip 142 is a handle 148. Once theproper dimensions of the disk space are determined, contacting memberswith the desired axial height 150 between the opposed axial contactingsurfaces 16 and lordotic angle can be selected to produce the desiredconfiguration in the assembled prosthesis. Preferably, prostheses withaxial heights from about 6 mm to about 30 mm, and with between about 0°and 20° of lordosis can be assembled. In the cervical spine, a height ofabout between 6 mm and 12 mm is preferred. In the thoracic spine, aheight of about between 6 mm and 20 mm is preferred. In the lumbarspine:, a height of about between 9 mm and 30 mm is preferred.

As shown in FIGS. 18 and 19, the embodiment of prosthesis 152 includes aprosthetic vertebral-body portion 154 for use after a corpectomy.Vertebral contacting members 156 are articulated via articulationportions 48,49 to the body portion 154. On an opposite axial side, thebody portion 154 is articulably associated with a another vertebralcontacting member 156 via a second set of articulation portions 48,49.The body portion 154 defines articular cavities 50 to pivotally androtatably receive the articulation portions 48 or 49.

The body portion 154 has major and minor openings 160,162 to promotebone growth and fusion therewith from remaining portions of the vertebraon which the corpectomy has been performed, and into which the bodyportion is being implanted. The hollow interior 164 of the body portion154 can be filled with a protein, bone, or other material to furtherpromote the bone growth and fusion. Additionally, suture openings 170can be provided to thread a suture therethrough or to pass anotherretaining member between the contacting portions 156 to retain the unitassembled.

The axial height 166 of the body portion 154 is preferably selected tobe about the height of a healthy vertebral body or of the vertebral bodyit replaces, although the body portion height 166 can be madesufficiently larger to position the articulations 46 in the desiredposition. Preferably, the combined height 168 of the prosthesis 152,measured between the axial contacting surfaces 16 of the contactingmembers 156 is preferably selected to be about the combined heightbetween the opposed vertebrae that are engaged with the contactingsurfaces 16, or of the healthy or desired height of a vertebral bodyplus the height of a disk on each axial side. Disk heights typicallyrange from about 4 mm to about 20 mm, and vertebra height typicallyranges from about 10 mm to 50 mm. The preferred height in the cervicalspine is about between 10 mm to 30 mm, in the thoracic spine is aboutbetween 20 mm and 60 mm and in the lumbar spine is about between 30 mmand 70 mm. The axial position of the articulations is also preferablyselected to provide the desired movement characteristics at the relevantportion of the spine.

Referring to FIG. 20, another prosthesis 172 embodiment for use with acorpectomy has a cylindrical body prosthetic portion 174 with angularopenings 176 to promote bone fusion. An articulation portion 178 can beof unitary construction with the body portion 174 or otherwise fixedthereto, or can alternatively be slideably associated with the bodyportion 174, such as by providing a key and keyway translationalarticulation. The articulation portion is pivotally associated with thecontacting members 156. In another embodiment, the body portion has arecess to receive a protrusive articulation portion in fixed associationwith the contacting member. A membrane 78, as shown in FIGS. 6 and 7 canalso be applied to corpectomy orthroplasty embodiments, as well as posts66.

Substantially the entire prosthesis can be made of a single material toavoid galvanic corrosion or from different materials to take advantageof the different material properties in different parts of theprosthesis. A preferred material for the contacting members,articulation portions, and any present body portion is titanium oranother durable and hard material. In one embodiment, the contactingmembers, articulation portions, and body portion, if employed, are madefrom a radiolucent material or are otherwise configured to reduce oravoid the production of radio artifacts in an MRI or in an x-ray. Assuch, the entire device or substantially the entire device can be madeof a polymer, such as PEEK. Alternatively, certain portions can be maderadiolucent, while others are not. This can be employed to producebetter images of the structure of the body without the prosthesisblocking portions of the image. Additionally, radiopaque markers 180,such as shown in FIG. 1, can also be employed in predeterminedradiolucent portions of the prosthesis to aid in its imaging, withoutinterfering significantly with the imaging of the surrounding tissue.Preferably, the contacting members, and articulation portions aresubstantially rigid.

Referring to FIGS. 21-24, the preferred embodiment of an inventiveprosthesis insertion device 182 is shown, which functions as a jig tohold an assembled intervertebral prosthesis 10. The insertion device hasopposed holding portions 184 that preferably come together along agenerally laterally facing vertical surface.

In the holding position of FIG. 21, the holding portions 184cooperatively and positively hold the prosthesis 10. This is preferablyaccomplished by the holding portions 184 cooperatively extending aroundthe prosthesis 10 to sufficiently to capture it to inhibit or preventremoval of the prosthesis 10 from the holding portions 184. Extensions186 extend around the ledges 18, for example, to trap the connectingmembers against a holding surface 188 that faces the extensions 186.Spacer lips 190 is also preferably provided to fit between thecontacting members 12,14 to hold and maintain a predeterminedorientation between articulated parts of the prosthesis 10 duringimplantation.

In the holding position, the holding portions 184 thus block exit of thecontacting members 12,14 preferably all directions. The holding portions184 can be separated, preferably laterally and in an unrestrictedmanner, to release the prosthesis.

The insertion device preferably also defines bores 192 for receiving andaligning a drill bit or a drill guide 194, as shown in FIG. 22, and thefasteners 24 and fastener driver 196, as shown in FIG. 23, while holdingthe prosthesis 10 in the desired implantation position in the spine. Thedrill guide 194 is preferably configured for automatic positioning at apredetermined depth in the bores 192, such as by providing an angledshoulder 198 to abut the outer surface of the holding portions 184.

The bores 192 are preferably defined cooperatively between the holdingportions 184 by employing a groove in the inside surface of one holdingmember 184 that faces a groove in the inside surface of the otherholding member 184, but the bores alternatively can extend completelythrough one of the holding members 184. In addition, the bores 194 forinsertion of the diagonally oriented fasteners 24 can cross each other,as can be seen from FIGS. 22 and 23.

A connecting member 200 is preferably associated with the holdingportions 184 to selectively maintain the holding portions 184 in theholding position and for releasing them therefrom after theimplantation. The preferred connecting member 200, shown in FIG. 24, isconfigured as a forceps with a hinge 202 that pivotally connects theholding portions 184. A scissor linkage with handles 204 hinged at thehinge 202 move the holding portions into and from the holding position.A locking mechanism 206 is provided, such as an actuate arm 208 thatextends from one side of the scissor linkage and that has ridges toengage corresponding ridges on the other side 210 of the scissorlinkage.

To implant the prosthesis 10 in an endoscopic or laparoscopic procedure,a surgeon preferably performs a disk resection or incises the annulus ofthe disk to create a window into which the prosthesis 10 can beinserted. The nuclear gelatinous core of the disk is removed, and thefaces of the endplates of the vertebral bodies are cleared of cartilage,exposing the cortical bone of the vertebral endplate. The cortex can bebreached in the center of the vertebral endplate, exposing cancellousbone.

The surgeon then inserts the prosthesis through an incision with theinsertion device 182, preferably in the anterior side of a patient'sbody. Once the prosthesis 10 is positioned between the vertebrae, thebone is drilled if fasteners are to be used, using a drill guide 194fitted in the insertion device 182. The fasteners 24 are preferablysequentially inserted into the insertion device 182 and inserted intothe bone, such as by rotating with a driver 196 placed in the insertiondevice 182.

In procedures in which the implantation is not conducted from ananterior side of the spine, contacting members can be used with flanges18 and fasteners 24 that are oriented an angle between the anterior andlateral sides, for instance. The fasteners can also be offset from theanterior side and can enter the bone at an angle from theanterior-posterior directions, when viewed along the spinal axis.

The preferred arthroplasty prosthesis is tolerant of implantationoff-center or out of alignment, as the contacting portions can beself-centering or aligning due to the bias by the ligaments andsurrounding soft tissue.

While illustrative embodiments of the invention are disclosed herein, itwill be appreciated that numerous modifications and other embodimentsmay be devised by those skilled in the art. For example, while thepreferred embodiments of the invention are described with aconfiguration for their use between vertebrae, another embodiment can beused at the end of the spine, such as adjacent the skull or betweenother articulated bones, such as in the appendicular skeleton. Thefeatures of different embodiments can be interchanged depending on thedesired characteristics of the assembled prosthesis. Therefore, it willbe understood that the appended claims are intended to cover all suchmodifications and embodiments that come within the spirit and scope ofthe present invention

1-45. (canceled)
 46. A vertebral arthroplasty prosthesis, comprising: afirst support member having a first anterior-posterior and lateralpivotal axis; a second support member having a second anterior-posteriorand lateral pivotal axis; and an articulation member including: a firstarticulation portion having a first pivotal joint member in pivotalassociation with the first support member for pivoting at the firstpivotal axis, and a second articulation portion having a second pivotaljoint member in pivotal association with the second support member forpivoting at the second pivotal axis, wherein the first and secondarticulation portions are associated with each other for translationwith respect to each other at a location between the first and secondarticulation portions to translate the first support member, firstpivotal joint member, and first pivotal axis with respect to the secondsupport member, second pivotal joint member, and second pivotal axis;wherein the first support member, articulation member, and secondsupport member are configured for cooperatively supporting vertebrae oneither side of the prosthesis of a spinal column; and wherein theprosthesis is configured such that, when implanted in the spinal column,the articulation member is disposed in a location corresponding to anintervertebral disk.
 47. The prosthesis of claim 46, wherein thearticulation member is configured for limiting a translational movementalong lateral and an anterior-posterior directions to a predeterminedrange.
 48. The prosthesis of claim 47, wherein the articulation memberis configured for limiting a pivotal movement along both the firstpivotal axis and the second pivotal axis to a predetermined range. 49.The prosthesis of claim 46, wherein the first and second articulationsportions are translatable with respect to each other to translate thefirst and second support members and pivotal axes with respect to eachother substantially uncoupled from pivotal movement of the first andsecond support members.
 50. The prosthesis of claim 46, wherein thefirst and second pivotal joint members are configured to provideuniversal pivoting of the first and second support members about thefirst and second pivotal axes, respectively.
 51. The prosthesis ofclaim, 46, wherein the support members have corresponding joint membersthat are associated with the first and second pivotal joint members toprovide a ball and socket joint for pivoting about each of the first andsecond pivotal axes.
 52. The prosthesis of claim 46, wherein thearticulation member is configured to permit relative axial rotationbetween the contacting members.
 53. The prosthesis of claim 46, whereinthe second support member comprises a body prosthetic portion, theprosthesis having an axial height corresponding approximately to theheight of a vertebra.
 54. The prosthesis of claim 46, wherein the firstsupport member comprises a first bone contacting member configured forengaging first vertebra of the spinal column, the first contactingmember comprising: a fastener mount portion configured for attaching abone fastener thereto; and vertebral contacting surfaces disposed andoriented for positioning an apophyseal ring of the first bone withrespect to the fastener mount portion in an attachment position forattaching the fastener from the fastener mount portion through theapophyseal ring to attach the first contacting member to the first bone.55. The prosthesis of claim 54, wherein the fastener mount portiondefines an opening for receiving a threaded surgical fastenertherethrough.
 56. The prosthesis of claim 55, wherein the fastener mountportion is oriented for inserting the fastener diagonally into theapophyseal ring.
 57. The prosthesis of claim 54, wherein the vertebralcontacting surfaces are oriented to capture axial and radial surfaces ofthe vertebral body for positioning the apophyseal ring in the attachmentposition.
 58. The prosthesis of claim 46, wherein the first supportmember comprises a vertebral contacting member.
 59. The prosthesis ofclaim 46, wherein the second support member comprises a vertebral bodyprosthetic portion.
 60. The prosthesis of claim 46, wherein the secondpivotal axis comprises an upper body anterior-posterior and lateralpivotal axis of the second support member, and the second support membercomprises a third pivotal axis comprising a lower bodyanterior-posterior and lateral pivotal axis of the second supportmember.
 61. the prosthesis of claim 60, further comprising: a thirdsupport member having a fourth anterior-posterior and lateral pivotalaxis; a second articulation member, including: a third articulationportion having a third pivotal joint member in pivotal association withthe second support member for pivoting at the third pivotal axis, and\ afourth articulation portion having a fourth pivotal joint member inpivotal association with the third support member for pivoting at thefourth pivotal axis.
 62. The prosthesis of claim 61, wherein the thirdsupport member comprises a vertebral contacting member.
 63. Theprosthesis of claim 62, wherein the third and fourth articulationportions are translatable with respect to each other at a locationbetween the third and fourth joint members to translate the second andthird support members and pivotal axes with respect to each other. 64.The prosthesis of claim 46, wherein the first and second articulationportions are in sliding contact against each other to allow thetranslation.
 65. An arthroplasty prosthesis, comprising: first andsecond support members configured for cooperatively supporting opposingarticulated bones, the first support member having a first atanterior-posterior and lateral pivotal axis, and the second supportmember having a second anterior-posterior and lateral pivotal axis; andfirst and second articulation portions, the first articulation portionhaving a first pivotal joint member in pivotal association with thefirst support member for pivoting at the first pivotal axis, and thesecond articulation portion having a second pivotal joint member inpivotal association with the second support member for pivoting at thesecond pivotal axis, wherein the first and second articulation portionsare in sliding contact with each other between the first and secondpivotal joint members to permit translation of the first and secondsupport members and pivotal joint members with respect to each other,wherein the prosthesis is configured such that, when implanted in thespinal column, the articulation portions are disposed in a locationcorresponding to an intervertebral disk.
 66. The prosthesis of claim 65,wherein one of the first support member and the first articulationportion defines a protrusion extending generally along an axis extendingbetween the support members, and the other defines a recess configuredfor receiving the protrusion to pivotally associate the first supportmember and the first articulation portion.
 67. The prosthesis of claim66, wherein one of the second support member and the second articulationportion defines a protrusion, and the other defines a recess configuredfor receiving the protrusion to pivotally associate the second supportmember and the second articulation portion.
 68. The prosthesis of claim66, wherein at least one of the recess and protrusion is taperedsubstantially about a spinal axes that extends axially between thesupport members.
 69. The prosthesis of claim 65, wherein the first andsecond articulation portions comprise blocking members juxtaposedradially with respect to a spinal axes that extends axially between thesupport members for abutting each other to limit the translationalmovement therebetween.
 70. The prosthesis of claim 65, wherein thesecond support member comprises a body prosthetic portion, such that thesupport members are pivotally and translationally moveable with respectthereto.
 71. The prosthesis of claim 65, wherein the opposingarticulated bones comprise first and second vertebra bodies, each havinga respective apophyseal ring, and wherein the first and second supportmembers comprise: an axial contacting surface oriented to abut andsupport an axial face of a respective one of the first and secondvertebra bodies; a radial contacting surface configured to abut a radialside of the respective one of the first and second vertebra bodies; andan apophysis receiving area between the axial and radial contactingsurfaces defining an apophysis groove that is disposed and configuredfor receiving the apophyseal ring of the respective one of the first andsecond vertebra bodies.
 72. An arthroplasty prosthesis for implantationin an implantation site between two non-adjacent bones of the axialskeleton, comprising: a vertebral body prosthetic portion configured forreplacing at least one vertebral body of a patient, the body prostheticportion having an upper body anterior-posterior and lateral pivotal axisand a lower body anterior-posterior and lateral pivotal axis; and upperand lower disk prosthetic portions, configured to replace at leastportions of two intervertebral disks disposed adjacent the replacedportion of the vertebral body, the disk prosthetic portions configuredto contact and support axial skeleton bones adjacent the implantationsite and being articulated with the body prosthetic portion, the upperand lower disk prosthetic portions respectively having a upper and loweranterior-posterior and lateral pivotal axes, wherein the upper diskprosthetic portion comprises: an upper support member having an upperfirst anterior-posterior lateral pivotal axis, an upper firstarticulation portion having an upper first pivotal joint member inpivotal association with the upper support member for pivoting at thefirst pivotal axis, and an upper second articulation portion having anupper a second pivotal joint member in pivotal association with thevertebral body prosthetic portion for pivoting at the upper body pivotalaxis, in contact with the upper first articulation portion between theupper joint members such that the upper first and second articulationportions are translatable with respect to each other wherein the lowerdisc prosthetic portion comprises: a lower support member having asecond anterior-posterior lateral pivotal axis, a lower firstarticulation portion having a lower first pivotal joint member inpivotal association with the lower support member for pivoting at thesecond pivotal axis, and a lower second articulation portion having alower second pivotal joint member in pivotal association with thevertebral body prosthetic portion for pivoting at the lower body pivotalaxis, in contact with the lower first articulation portion between thelower joint members such that the lower first and second articulationportions are translatable with respect to each other; and wherein thebody and disk prosthetic portions and the articulation members areassociated for cooperatively carrying spinal loads at the implantationsite.
 73. The prosthesis of claim 72, wherein both of the of the supportmembers are configured for engaging a respective axial skeleton boneadjacent the implantation site.